The transit agency sent the union a memo Monday, saying the work stoppage is prohibited and that anyone who called out sick on Monday will not get paid sick leave unless it is verified and advised them to stop this slowdown.

Two-thirds of the Muni system buses were parked in the yard. Light rail, cable and trolley cars were idled as Muni operators called in sick.

"About 400 out of 600 morning runs are not out today. So what we're trying to do is balance service the best that we can throughout the systems," Muni spokesman Paul Rose said.

There was no advance warning so passengers were caught off guard.

"I waited for about 30 minutes. It was a bit upsetting, but alright. I mean, what can we do? Just deal with it," said Muni rider Evelyn Moran said.

The Transport Workers Union, which represents the 2,000 operators, is involved in a contentious contract dispute. A recent newsletter to members said, "We are truly confused with the disdain SFMTA has... Why do they hate us so much?"

One driver ABC7 News spoke to, who did not want to be identified, showed up to drive the 39 bus near Fisherman's Wharf. He fully supports his union and said, "We're out here doing a job, but you just want to be compensated. That's all it is to be fair and equitable."

On Friday, the operators voted overwhelmingly to reject the city's latest offer which proposed just over 11 percent in wage increases over two years. That would push pay to $32 an hour July 1, making Muni operators the second highest paid transit workers in the nation. But employees would be asked to contribute 7.5 percent into their pensions, which is currently paid for by the city.

San Francisco Mayor Ed Lee says everyone is paying in. He said, "That's what we did with pension reform two years ago when we put it before the voters. We all agreed we would pay more. I'm paying more, so is everyone else around me."

The mayor says he sympathizes with the riding public and if no agreement is reached with the operators, there will have to be arbitration.

BART helped by honoring Muni fares in San Francisco and Daly City.

Cable cars are also not running because of the labor dispute, but buses are in place for those routes. Tourists are arriving at Market and Powell hoping to hop on a cable car, but no operators means the iconic mode of transportation is sitting in park.

"We're very disappointed and we won't feel that we've seen San Francisco probably because we haven't been on the old cable car," said Heidi Edman, Australia.

Police officers were moving tourists about a block away to Ellis and Powell where a shuttle bus would pick them up and take them through San Francisco along the same cable car route.

The good news for people who end up on a shuttle bus is they don't have to pay the $6 cable car fare, just the $2 bus fare.